Strange interaction at work and no one else sees the issue?

Yes, precisely this.
Whatever the reasons for the behaviour, an adult who is competent enough to hold down a job should know when this behaviour is acceptable and when it isn't. It is very clearly not acceptable at work, in a fairly serious albeit informal chat with your manager about your actions.
Saying anything else simply IS excusing him.

What are you going to do @FionnulaTheCooler ?

point one is that I don't think that that behaviour is acceptable regardless of whether the person is a "good natured joker" or a misogynistic asshole. If its the first, then he should have learned a long time ago that such behaviour is not appropriate at work; if the second then there is no mitigation. I agree that its arguable that the consequence could vary according to which it is but either way "that's how he is" is no excuse.

Agree

I'm not excusing him, I do not know the person or the full details of the situation. Offering possible reasons/motives for someone's behaviour is not the same as defending them. I'm answering the op in a hypothetical way, depending on the specifics of the scenario - which are not entirely clear.

You have a particular interpretation of the scenario (others seem to have interpreted it very differently). My advice covered both interpretations, its up to the op to decide which fits her actual situation.

No, you ARE excusing him. Whether or not his other colleagues believe him to be a 'good-natured joker', in a work context, especially a work context where there's a serious discussion with your manager about your behaviour imminent, this behaviour is by definition 'of a more challenging nature'.

I'm not excusing him, as human beings we all have faults and failings, and as managers we are there to deal with that appropriately and proportionately based on the individual and the context.

The comment about him being "just like that" is not clear as to whether it's meant he is a good natured joker, or whether his behaviour is of a more challenging nature. The second scenario should obviously be dealt with seriously, and if he was also the aggressor in the argument (which I don't think op actually says) it suggests he needs to be on some sort of performance management.

trying to diffuse what was probably a stressful situation for him, as he was expecting to be reprimanded
Diddums. He's a grown man and if he can't take the 'stress' of a quiet chat with his boss then he is possibly in the wrong job/environment.
In any case, if you read the OP properly you'll see it says that the OP's manager said 'that is just what that colleague is like.' So his attitude is clearly known about, and tolerated.

There are two ways of looking at it.

It might have been his (immature) way of acknowledging he was in the wrong and trying to diffuse what was probably a stressful situation for him, as he was expecting to be reprimanded. If he is normally jokey and fairly 'harmless' good-natured guy, I wouldn't take his reaction too badly. I would just remind him that I do expect him to take something like this more seriously, and not to do anything like it again.

The other possibility is that he was trying to shock you and put you on the back foot. If he's a more difficult character at work it could be one of his manipulation tactics to belittle someone and show his disregard for seniority. In this case I would tell him that I would be watching his behaviour closely and I wouldn't want to see any more inappropriate behaviour, otherwise I'd be reporting him (and I would make a record about what he did with HR).

So, what is he like at work? And how serious was the fight he was involved in?

So, what have HR said @Teachnomore ?

I’d love to know if he was harassing the other team member and she lost her cool.

If there was an incident between 2 colleagues in work and you got an email from your senior and this guy was one of them. Chances are there is an issue with this guy and it's not only you!

I would also argue it is sexual harassment.
As far as I know adults only spank each other on the bum for sexual reasons.

He’d never have done it to a man because it could have been taken as an invitation to fuck him.

Yes. I would LOVE to hear about the dispute that prompted the disciplinary.

Go read up on the difference between sexual harassment and harassment relating to sex and come back to me.

He only did this because she is a female. There’s no way he’d have done this if it was a male boss.

If he’s inappropriate to his manager he’s probably even more inappropriate to female staff who aren’t senior to him.

This

And without it being appropriate in a disciplinary interview.

It's quite possible to have banter, light hearted fooling around, laughs with colleagues and bosses, without veering into inappropriate sexualised or sexist/misogynistic territory.

We’ve also lost sight of the other person involved in the original dispute that started this whole process off. What’s happened to her?

This. I would make it clear you tried to fact find and de escalate the conflict but colleague has shown himself unable to cooperate and showed further inappropriate behaviour.

Yes they dont sound male they are male.

There are usually differences but there are also the sort who use bizarre or OTT jokes with both sexes.

That was the point I was making, they’re male so more likely to excuse the behaviour than if she’d spoken with a female who would have said it was inappropriate

You’re right, he may speak with a male manager like that however in my experience of over 20 years in the workplace, men treat and speak to women differently than they do other men in the workplace

I told my manager what happened, who basically shrugged his shoulders and said that is just what that colleague is like

Which is exactly why this needs to go to HR, formally.

1. because it is incredibly inappropriate in itself
2. because it clearly isn't out of the ordinary for him
3. because the colleague he was originally arguing with last week needs to be supported and
4. because YOUR MANAGER seems to think this is an okay way to behave, not just in the workplace generally, but in a meeting he was at to discuss an altercation that he had already been involved in.

What happened today @Teachnomore ?